Distributing valve



June 22, 1937. E. G. CARLSON 2,084,477

A DISTRIBUTING VALVE Filed Aug. 26, 1953 @aux INVENTOR ERT UARLO/v 50/ liv!! C, HIS ATTORNEY.

Patented June 22, 1937 NETE@ STATES ement OFFICE to Sperry Gyroscope Company, Inc., Brooklyn,

N. Y., a corporation of New York Application August 26,

8 Claims.

This invention relates to means for supplying the proper air pressure (usually negative pressure) to air driven instruments on aircraft. At present most commercial and military airplanes are equipped with several navigational and atti'- tude indicating instruments, most'of which are air driven. Among such instruments may be mentioned the turn indicator, the directional gyroscope -and the artificial horizon. l The presw ent practice is to drive such instruments by withdrawing air from the casing of each instrument by a separate vacuum pump for each instrument. Usually such a pump is in the form of a venturi,

l l, each instrument having its own venturi on account of the varying air requirements of each instrument. Much difficulty has been experienced with Venturi tube pumps on account of varying atmospheric conditions due to rain, sleet, snow and cold.

According to the present invention it is proposed to drive al1 such air driven instruments from the vacuum supplied at the intake side of the aircraft engine. I have found experimentally that an ample negative pressure may be obtained with the modern supercharged transport engine to operate all air driven instruments. Such a source could not be used directly, how@- ever, on account of the great variations in vacuum that occur. The purpose of the present invention is to provide an automatic regulating valve for insertion between the engine manifold and the instruments which will supply substantially uniform pressure to the instruments in ac# cordance with the requirements of each.

d l Referring to the drawing showing several forms my invention may assume, Fig. 1 is a view of the panel of an aircraft showing the various air or pressure driven instruments and indicators connected through my regulating valve to the engine.

Fig. 2 is an end elevation of my regulating valve.

Fig. 3 is a longitudinal section of the same.

Fig. 4 is a longitudinal section of a simpler form of regulating valve.

Referring to Fig. 1, the aircraft engine is represented at I. A pipe 2 may be tapped into the intake side, preferably between the carbureter A, and supercharger (not shown) where the pressure is the lowest. The air will, therefore, be

drawn rapidly through said tube into the supercharger and on to the engine. Said pipe leads into the casing 3 of my regulating and distributing Valve. Said casing is shown as provided with a main longitudinally extending chamber 4 1933, serial No. 686,927

which is normally separated from the chamber 5 where the pipe 2 enters the casing by a safety valve 6 held lightly on its seat by a weak spring l. As soon, however, as the engine is started, the withdrawal of air through thepipe 2v causes the valve 6 to open against the spring, said valve remaining open as long as the engine is'operating unless back re occurs, which will immedi-J ately closethe valve B and prevent positive air pressure from reaching the aircraft instruments and also preventing oil and soot from being blown into the instruments. Valve 5 may also operate as an adjustable throttle as hereinafter described. For this purpose the valve 6 is shown as provided with a stem 8 slidably mounted in Ythe threaded member 9 which closes the chamber 5, saidstem operating to limit the opening of the valve 6 by contact with the set screw Il) threaded in the outer end of the member 9 and which may be locked in place by the lock nut Il. The chamber 5 may be directly connected through a bore l2 and pipe I3 to the engine Vacuum gauge I so that the gauge will show the true vacuum uninuenced by any throttling that mayrtake place at the valve 6. Beyond the valve 6 the chamber 4 is shown as provided with a longitudinally extending slot l5 which communicates with a channel i8 leading through the several outlets to the aircraft instruments. bodiment shown there are four such outlets', i. e., `Il .which is connected by YVa pipe I8 to the turn indicator I9, .20 connected by a pipe 2| to the articial horizon 22, 23 connected by apipe 24 with the directional gyroscope 25, and 26 cone' nected by a pipe 2l with the vacuum gauge 21 f to show the operating pressure available at the valve for the instruments. Preferably the sizes of the openings Il, 2l), 23 and 26 are varied in'ac-E cordance with the requirements of each instrument so that the requisite pressure is maintained on each. Thus the aperture 20 for the artificial horizon is shown as larger than that for the other instruments because it requires more air to drive the same. Also manually operated valves 28 may be provided in the pipes to adjust for the individual requirements of each instrument.

Within the chamber 4 I mount the main regu# lating valve 29 which is shown as in the form of In the em-l a piston yieldin'gly pressed to the left in Fig.v 3

byoone or more coil springs'll. The outer 'face 3l of said piston is normally open to the atmosphere through screened opening 32 in casing 3 so asyto be subject to atmospheric pressure. Obviously asthe pressure falls within the chamber Yll, a i,

point will be reached Where the atmospheric pressure on the piston will overcome the spring tension andgforce the piston to the right to partially close the slot I5 in accordance with a function of the difference in pressure Ywithin and without the casing. Preferably the spring is so designedas to yield at a predetermined negative pressure, for example about 6" orV 8" kof mercury on the gaugel 21 so that as the pressure rises above that the valve will be gradually closed to prevent a greater negative pressure from reaching the aircraft instruments.

Preferably I employ spring means, the tension of which increases more rapidly thanthe extent of compression on account ofthe fact that the power obtainable Varies roughly with the square of the pressure. As shown, three springs are employed, the first spring 33 being a light spring, the next spring 34 of intermediate stiffness, and

the last spring 35 still stiffenthe springs being shown as separated by Washers 36.

, If the valve is designed to operate the instrument at the proper speed when the aircraft engines are operating at normal speed, it is probable that the piston valve 29 will become entirely l closed when the engines are idling onthe Vground on account ofthe greatV increase in vacuum amounting to several hundred percent between two. operating conditions. While, ofcourse, itis not necessary to operate most of the aircraft instruments when the aircraft is on the ground, it may be desirable to bring all instruments up to speed. at that time. For this purpose a small hole 31 may; be bored between the chamber 4 and I6 beyond the range .of the jpiston 29 so that said hole is never closed. Y Y

The purpose of the adjustable stop I0 for the valve B is to furnish a quick adjustmentfor securing the proper operating conditions at greatly varyingv altitudes` Thus at low `altitudes alessV difference of pressure is required than at high altitudes on accountA of the rarity of the air in theY latter case.v Therefore, if the. valve 29 be Vdesigned to operate at the greater difference in pressure, say 6" or 8,` of mercury, the operator may readily reduce the operating-pressure when flying at low altitudes by screwing in on the set screwv l0 so as to prevent the valve B from open.- ing more than an amount 'sufficient to secure the proper differential pressure, say 4". to 6" of mercury, the valve 6 thus acting asa reducing throttle. s Y

The form of the invention shown in Fig. 4is substantially identical in principle with the form shown in Figs.2 and 3 except that fewer outlets are shown, one to a turn indicator,V one toanV artificial horizon or directional gyroscope, and

one to the vacuumgauge. Also, operating pressure is, maintained during engine idling, in this caseby providing a longstem 4D extending from the set screwlll, the end of which is adapted to engage theinterior of the .piston 29' Yto prevent the same from entirely closing the slot I5 under any conditions. Also the adjustment for altitude changes in this case is made by varying the spring tension ofV spring Sli.L To this end the set screw 4l may be advanced to increase the tension and locked inoplace by lock nut Il', thus advancing the collar 42 which said spring engagesfor high altitude flights. Y 1

In accordance with theprovisions of the patent statutes, I have herein described the principle andoperation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof, but I desire to have it understood that the apparatus shown is only casing.

illustrative and that the invention can be carried out by other means. Also, while it is designed to use the various features and elements in the combination and relations described, some of these may be altered and others omitted Without interfering with the more general results out# Y lined, and the invention extends to such use.

Having described my invention, what I claim and desire to secure by Letters Patent is:

l. A control valve gear for supplying negative air pressure to the air driven instruments of aircraft from the engine intake comprising a hollow casing having a plurality of outlets adaptedrto be connected respectively to the engine and to the one or more instruments, a reducing piston valve between the engine intake andthe instrument outlets, spring means for biasing said piston against atmospheric pressure on the outer end Y thereof whereby decrease in the pressure in said casing below a predetermined amount will restrictthe opening in said valve, and valve kbypass means provided between the engine intake and the instrument outlets whereby Va desired vacuum is always supplied to the instruments rebiased to a closed positionl and held open by thek engine suction, a pressure regulating valve also between said engine intake and said instrument outlets, and means for insuring continuous communication between said engineintake and said instrument outlets whereby suction is continuously applied to the instruments.

3. A control valve gearfor supplying `negative craft from Vthe enginerintake comprisinga. holilair pressure to the air driven instruments of airlow casing having a pluralityof outletsadapted to be connected respectively to the engine and to the one or more instruments, a safety valve between said engine intake and the other intakes biased to a closed position and held open by the engine suction, and a pressure regulator between said safety valve and Vsaid instrument outlets, said regulator comprising a slot in said hol.- low casing and a piston valve responsive to atmospheric pressure and the pressure within said 4. A control'valve gear for supplying; negative air pressure to the air driven instruments of aircraft from the engine intake comprising a hollow casing having a plurality of outlets adapted to be connected respectively to the engine and Y pressure to aircraft instruments from the aircraft engine intake comprising a hollow casing, a pressure responsive regulator for preventing the negative pressure supplied to the instru` ments from exceeding a predetermined amount,

said regulator comprising a slot in said hollow casing and a piston valve responsive to atmospheric pressure and the pressure within said casing, and means for preventing the complete shutl off of pressure to said instruments when the engine is idling.

6. A control valve gear for supplying negative air pressure to the air driven instruments of aircraft from the engine intake, comprising a hollow casing having a plurality of outlets adapted tobe connected respectively to the engine and to the one or more instruments, a reducing valve between the engine intake and the instrument outlets comprising a piston within said casing exposed at one end to the atmosphere and a spring yieldingly holding said piston in its open position, said piston operating to gradually shut off the connection between said engine intake and instrument outlets as the vacuum at the engine increases, and manually adjustable valve means between said reducing valve and the engine intake, said valve means cooperating with said reducing valve to maintain reduced pressure in the instrument outlets regardless of momentary failure of engine suction.

7. A control valve gear for supplying negative air pressure to the air driven instruments of aircraft from the engine intake comprising a hollow casing having a plurality of outlets adapted to be connected respectively to the engine and.to

the one or more instruments, and a reducing valve between the engine intake and the instrument outlets comprising a piston within said casing exposed at one end to the atmosphere, a spring yieldingly holding said piston in its open position, said piston operating to gradually shut on the connection between said engine intake and instrument outlets as the vacuum at the engine increases, and a restricted by-pass opening between the engine intake and instrument outlets beyond the range of movement of said piston for preventing the shutting off of pressure to said'instrinnents when the engine is idling.

8. A control valve gear for supplying negative air pressure to the air driven instruments of aircraft from the engine intake comprising a hollow casing having a plurality of outlets adapted to be connected respectively to the engine and to the one or more instruments, a safety valve between said engine intake and the other intakes biased to a closed position and held open by the engine suction, a reducing valve between said safety valve and said instrument outlets, said reducing valve comprising a slot in'said hollow casing and a piston valve responsive to atmospheric pressure and the pressure within said casing, and variable means for limiting the extent of opening of said valve with altitude changes.

BERT G. CARLSON. 

